Commutator



De@ 25, R93@ H WEICHSEL lju?.

COMMUTATOR Filed Oct. 9, 1929 Figi, 3L o Invent @1 Patented Dec. 2, 1930 UNITED STATES PATENT OFFICE HANS WEICHSEL, OF ST, LOUIS, MISSOURI, ASSIGNOR T WAGNER ELECTRIC CORPORA- i TION, OF ST. LOUIS, MISSOURI, A CORPORATION OF DELAWARE COMMUTATOR Application filed October 9, 1929.

My invention relates to a commutator for dynamo electric machines and its object is to provide means for increasing the effective life of a commutator and reducing brush wear.

The invention also reduces the cost of manufacture.

The usual practice in constructing commutators is to insulate the segments from each other by means of sheets of mica or other rigid material, which is not affected by the commutation sparking, and when the segment surfaces are worn by the effects of spark burning and friction, the brushes contact with and are lifted by the mica, resulting'in a great increase in sparking and in the wear of the .brushes and commutator. This soon necessitates under cutting the mica to again bring its edge below the surface of the commutator segments. This under cutting is not 2o only expensive but often causes the production of objectionable brush noise.

By my invention the insulation between the segments is automatically kept low enough not to interfere with the brushes but not too low to cause the development of the brush noise which results from such condition. I achieve this result by employing a segment insulating material which will be disintegrated by the commutation discharges between the a0 brushes and the commutator. The insulating material may be such that it is caused to disintegrate either by the heat of the sparks, or by self-combustion resulting therefrom.

In the accompanying drawings Figure l 1s u the end view of a portion of a cylindrical commutator made in accordance with my invention showing the commutator as originally constructed, and Figure 2 illustrates the condition immediately resulting from use.

Referring to Figure l, the commutator segments 2 are insulated from each other by sheets of a disintegratable material 3, such as compressed paper material commercially known as leatheroid, these sheets being permitted to extend to the periphery of the commutator as manufactured. When the commutator is placed in operation the commutation sparks produce a burning eiect which deteriorates the edge of the insulation material to a slight depth, and the resulting ash Serial No. 398,500. I

which may not be thrown off by the motion` of the commutator, cannot cause an elevation i of the brushes as they pass 'over it. As the'- surface of the commutator wears, the spark discharges cause further disintegration of the insulation, with the result that the upper edge of thc portion of the insulation which isf; capable of maintaining a physical separation" between the commutator segments, retreats in proportion to the wear of the commutator and, therefore, throughout use the distance from the upper edge of the insulation to the periphery of the commutator automatically remains substantially constant.

Tests have indicated that by employment of insulating material of the kind described, the commutator life will be approximately ten times that of a commutator having mica insulation.

The ash produced by the charring of leatheroid insulation is slightly conductive but in all machines in which the voltage between commutator segments is not high, the small current passing between segments through the portion of this ash which may not be removed by the action of the brushes or centrifugal force, does not adversely aiect the operating characteristics of the machine. One very desirable application for commutators made in accordance with my invention is in so-called repulsion induction motors in which there is small voltage between segments during the starting period when the brushes are operative, and tests show that the speed torque characteristics of these machines are not influenced by the very small current which may pass from segment to segment by means of the burned edge of the leatheroid.

While I have mentioned leatheroid as a suitable insulating material for the purposes of my invention, it will be understood that any material which will become disintegrated under the influence of the commutation spark discharge, will be satisfactory, provided the disintegrated material has a relatively high electrical resistance. By the expression capable of being disintegrated, or equvalent, used in some of the accompanying claims, I refer not only to combustible insulating material, but also to any other incharred portion below the brush contacting sulating material which will be reduced to granular, powdered, or like condition adjacent the eriphery of the commutator bg the electricalp effects of the cooperation o the brushes with the commutator.

Having fully described my invention, what -I claim as new and desire to secure by Letters Patent of the United States is:

1. A commutator for dynamo electric machines comprising conducting segments separated adjacent their brush contacting ends -by insulating material the entire thickness of which is subject, during commutator wear in operation, to such progressive disintegration under the influence of the electrical eects of the interaction of the commutator and brushes as will cause the outer limit of the undisinteated portion to be lowered upon the wearlng down of the brush contactmg surface of the commutator.

2. A commutator for dynamo electric machines comprising conducting segments separated adjacent their brush contacting ends by insulation which is of such material only as is capable of being disintegrated by commutation sparking at such rate, that during wearing down of the commutator in operation, the outer limit of undisintegrated portions of the insulating materia-l will be maintained below the level of the brush contacting faces of the segments.

3. A commutator having the brush contacting ends of its segments se arated by insulation consisting solely of f1 rous sheet material capable of beingcharred by commutation sparking at such rat'e as to autormatically maintain-the outer limit of the unface of the commutator during the wearing down of the commutator in service.

In testimony whereof, I hereunto ailix my signature, this 4th day ofOctober, 1929.

p HANS WEICHSEL. 

